1. Field of the Invention
The present invention relates to a display device, and more particularly to a display device which has white plates arranged in a two-dimensional array so as to correspond to pixels and a plurality of colored films stacked on the white plates and which effects color display by adjusting the way these films are stacked to color pixels to a given color.
2. Description of the Related Art
Display devices for use with portable information processing apparatuses for which there has been an increasing demand, are required to be thin, lightweight, and less power-consuming. Liquid-crystal display devices, plasma display devices, and flat CRTs have been known as thin display devices. Of these, liquid-crystal display devices are the most suitable from the viewpoint of power consumption, the most important of the above three requirements, and have been widely put to practical use.
Display devices generally have the direct viewing type that allows a person to see the display screen directly and the projection type that projects the image onto a screen. The direct-viewing-type liquid-crystal devices have the transmission type that has a light source (a back light), such as a fluorescent lamp, built in at the back and the reflection type that makes use of ambient light. Since the former needs a back light, it is unsuitable for low power consumption design. Therefore, the latter, the reflection type, is the most suitable for the display device for portable information processing apparatuses.
In the reflection-type liquid-crystal display device, a twisted Nematic mode liquid-crystal display is placed on a reflection plate so that it is not necessary to provide a back light. Therefore, a power consumption thereof is lower than that of the transmission type.
Such a reflection-type liquid-crystal display device has the following display modes: the ECB (Electrically Controlled Birefrigence) mode, the GH (Guest Host) mode, and the TN (Twisted Nematic) mode.
When the ECB mode or the TN mode is used, a polarizing plate is required. Since a polarizing plate has a transmittance of about 40%, the light use efficiency is low.
When the GH mode is used, a polarizing plate is not needed. In this case, however, electrodes of ITO (Indium Tin Oxide) whose transmittance is about 90% are formed over a very wide area, so that the light use efficiency is not very high.
The low light use efficiency and the low aperture rate decrease the luminance, making the display image darker.
As described above, the reflection-type liquid-crystal display devices are most suitable for display devices for portable information processing apparatuses which are required to be small and less power-consuming. They, however, have the problem that they have a low light use efficiency and a low aperture rate decreases the reflection luminance, making the display image dark.